It is a primary object of the invention described and claimed in my copending application Ser. No. 895,199 to provide an electron beam memory system having for the first time an electrostatic gun capable of developing high enough electron probe current densities to permit no-develop recording and small enough proble diameters to permit ultra-high density recording and yet of such low mass and compactness as to make feasible rapid random accessing of any area on the system's recording medium.
There is a need in such systems for dynamic beam deflection or positioning means in order to provide the very fine beam position adjustments required for track selection and tracking. There also exists a need for stigmating means for removing cross-sectional asymmetries in the electron beam.
To achieve the low head access times targeted, the electrostatic gun described and claimed in my copending application Ser. No. 895,199, is disclosed as having an axial length of 0.5-1.0 centimeter or less and a mass of 20 grams or less.
In the context of such a system, a deflection and/or stigmatizing system is needed which is ultra-compact and of ultra-low mass.
Beam deflection and/or stigmating systems are known which comprise deflection and/or stigmating coils wound on a mandril or otherwise supported between the gun exit and a beam focus. Other systems are known in which plural foci are formed in the beam path and the deflection and/or stigmating system is located intermediate two of such foci. Such systems are commonly provided in electron beam systems wherein the focus is formed so close to the exit point from the electron gun as to not permit the use of conventional beam deflection and/or stigmatizing means.
In each of such systems, the deflection and/or stigmatizing coils and coil mounting structures add to the mass of the beam generating system. Such conventional deflection and/or stigmating systems are deemed to be unacceptably large and massive for a fast-access electron beam memory system of the type identified above.
In electron guns or electron beam devices of the type having a beam deflection and/or stigmating system located intermediate two foci, the gun or head itself is much too long and massive to have any applicability to the fast-access electron beam memory system of the type described.
To the end of achieving the desired high electron probe density and small probe size, the above-identified ultra-compact electrostatic electron gun may provide a magnification of the electron source of 0.5 to 2.0. Image distances may be in the order of only a few millimeters. No conventional deflection or deflection/stigmating system is known of the type located between the gun exit plane and the beam's focus, which is compact enough to fit within this extremely small space.
Aside from electron beam memory applications, there is a need for a system capable of modifying an electron beam, as by dynamically or statically deflecting it and/or stigmating it, or otherwise, which can be integrated with an electrode gun to provide the beam modifying without adding to the axial length of the gun assembly.